Open Firmware

Contents

Introduction

In 2006 the company of Open Firmware inventor Mitch Bradley, Firmworks, Inc, released their Open Firmware implementation (OFW) under a BSD license. This code shares some code with SUN's OpenBOOT implementation. The open source OFW supports x86, PowerPC, and ARM architectures. Other architectures, including SPARC and MIPS, may be added as time and interest dictate.

The x86 version is used on the OLPC "XO" computer. The x86 version can be configured for numerous other environments, including

Direct QEMU ROM (replacing the "bios.bin" that is supplied with QEMU

Coreboot payload

Loadable on directly on top of a conventional PC BIOS (booted from floppy or hard disk like an OS). In this configuration it can run on an arbitrary PC, or on an emulator like QEMU, VirtualBox, or VMWare.

OFW can boot Linux directly from a disk file (FAT, ext2, ISO9660, or jffs2 filesystems) without the need for an intermediate bootloader like LILO or GRUB. The Linux image can be in either ELF format (as created by the first phase of the Linux kernel compilation process) or in the "bzImage" format that "wraps" the ELF image. When booting an ELF image, OFW can read the ELF symbol table so OFW's assembly language debugger can resolve kernel symbols.

OFW can also boot other ELF standalone images, providing to them rudimentary "libc" capability. That facility has been used for booting, for example, Minix, ReactOS, Plan9, Inferno and SqueakNOS. The OLPC system ROM includes several such "standalone client programs", including MicroEMACS, memtest86, and NANDblaster (a facility for fast OS updates over multicast wireless).